Dual-wavelength nonlinear sound pressure demodulation method and system for optical fiber FBG hydrophone

Abstract

The invention discloses a dual-wavelength nonlinear sound pressure demodulation method and a dual-wavelength nonlinear sound pressure demodulation system for an optical fiber FBG hydrophone. The dual-wavelength nonlinear sound pressure demodulation method comprises the steps of: 1) acquiring two paths of reflection spectra; 2) setting operating wavelengths of two paths of laser devices; 3) performing reflective spectrum phase conversion and curve fitting, and solving an inverse function; 4) determining wavelength translation amounts separately; 5) and demodulating nonlinear sound pressure according to a coupling model. The dual-wavelength nonlinear sound pressure demodulation system comprises the optical fiber FBG hydrophone, the two paths of wavelength tunable laser devices, an optical fiber coupler, an optical fiber circulator, a wavelength division multiplexer, two photoelectric detectors and a data acquisition card. The dual-wavelength nonlinear sound pressure demodulation method and the dual-wavelength nonlinear sound pressure demodulation system provided by the invention have the advantages of being free of theoretical sound pressure demodulation upper limit, being high in demodulation precision, overcoming blur direction, being flexible in demodulation, being capable of evaluating the accuracy of the demodulation result and the like.

Description

technical field [0001] The invention belongs to the technical field of optical fiber sensing, and in particular relates to the sound pressure demodulation technology of a hydrophone. Background technique [0002] High intensity focused ultrasound (HIFU) has received extensive attention in recent years and has developed rapidly. First of all, HIFU can be used as a new research platform in the fields of medicine, physics, chemistry and materials science. Secondly, HIFU is an extreme condition in the field of acoustics. Its major innovative research in various fields is no less than the extreme conditions that we are familiar with, such as ultra-high pressure, ultra-vacuum, strong magnetic field, strong radiation, high and low temperature. It is of great significance to promote the development of science and technology and social economy in our country. As the sound pressure is the core parameter of HIFU, it is extremely important to accurately measure and demodulate the soun...

AI Technical Summary

Problems solved by technology

This method has the following disadvantages: 1) Since the linear range is very narrow, the sound pressure demodulated after exceeding the linear range is obviously smaller than the actual sound pressure, resulting in large calculation errors; 2) Since it is a linear demodulation method, the light intensity signal output has 3) There is a problem of direction ambiguity, that is, when the light intensity changes near the peak of the reflection spectrum, the fiber optic FBG hydrophone will be extremely insensitive to the translation of the reflection spectrum, and the translation of the reflection spectrum will be almost insensitive. It causes changes in the light intensity signal, and it is not possible to determine whether the reflection spectrum is shifted towards an increase or decrease direction; 4) It cannot be flexibly demodulated, because the positive and negative sound pressures are usually asymmetrical, and the reflection spectrum caused by positive and negative sound pressures is left and right The amount of translation is also different, resulting in a large difference in output light intensity; 5) It is impossible to evaluate the accuracy of the demodulated sound pressure results

Limited by these five problems, the fiber optic FBG hydrophone is greatly limited when it uses the best linear bias point direct measurement method for sound pressure demodulation

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